The present invention relates in general to means for locking safety belt retraction mechanism of the type wherein a strap acceleration responsive means senses strap acceleration of more than a predetermined amount to cause lock up of the safety belt webbing storage against further belt protraction. More particularly, the present invention relates to an improvement in the means for activated the locking pawl in response to the strap acceleration sensor means including the provision of an improved construction, mode of operation and method of assembly of the programming pawl, pawl biasing spring and inertial mass relative the associated components of the safety belt retraction mechanism.
Safety belt retraction mechanisms are currently in wide use for restraining vehicle passengers in their seats during emergency conditions. Such mechanisms typically sense an emergency condition by sensing changes in inertia of the vehicle, or changes in the movement of the safety belt positioned about the passenger. In the latter type retraction mechanism, acceleration of the safety belt of more than a predetermined amount causes lockup of the safety belt retraction mechanism. In such belt sensitive retraction devices, the sensitivity of the acceleration sensing means is usually controlled by the provision of a calibrated spring which normally biases a component of the mechanism to a nonactivated position. Spool acceleration of more than a predetermined amount, causes the inertial mass to lag spool rotation and overcome the spring bias to cause the mechanism to lock up the retractor device. Exemplary of such a safety belt retractor is that of the European patent application publication No. 0,092,407 published Oct. 26, 1983, entitled "EMERGENCY LOCKING VEHICLE SEAT BELT RETRACTOR". The retractor of this publication, generally known in the art as a European type retractor, has a safety belt storage spool which can be locked against protraction through the operation of either a vehicle inertia sensor or strap acceleration sensor associated with the spool. In the spool of this prior retractor mechanism, the inertia mass is biased by an associated spring to a nonactivated position. Other devices have employed springs of various configuration for biasing various components of the mechanism which must be overcome to cause lockup of the device.
It is been found to be difficult to control and maintain the required level of calibration during manufacture for the springs employed in these types of devices. The assembly of the generally fine spring elements also has proven difficult from a retractor assembly standpoint and is critical to the sensor operation. It has been noted that it would be desirable to have a spring design such that it would be easy to assemble into the retractor mechanism, cooperate with the associated components in a repeatable and reliable manner and have a configuration which facilitates its construction, mode of operation and assembly. The same is true for the associated elements which comprise the inertia mass and the programming pawl which is provided to act in response to relative rotation between the inertial mass and spool to cause the programming pawl to engage an associated lock cup to operate a main locking pawl of the retraction mechanism.